1. Field of the Invention
The present invention relates to apparatus for controlling the transmitting power over a digital radio channel between at least one transmitting station and one receiving station, and providing information relating to the received signal to the transmitting station by means of a return channel. Such apparatus comprises, inter alia, at the receiving station, a threshold device for measuring the level of the received signal and providing information relating to the level of the received signal and, at the transmitting station, control means to increase or decrease the transmitting power in in response to such information over a given dynamic control range.
2. Description of the Related Art
Apparatus of this kind for controlling transmitting power is known from U.S. Pat. No. 4 004 224, assigned to the Siemens company.
In this patent control of the transmitting power is a function of a criterion corresponding to the level of the received signal. The fact that this sole criterion is employed has several drawbacks. A first drawback emerges from the fact that no account is taken of the quality of the received digital signal, i.e. of the error rate present in the received digital signal; in fact, the transmitting power is automatically increased in order to maintain a constant received-signal level, even if the value of the transmitted power necessitates operation in a non-linear range. The choice of this criterion is incompatible with the desire for a lower error rate and thus for a high signal quality which is necessary for present-day digital radio systems. A second drawback is that power regulation of this kind takes into account only disturbances inherent in the regulated transmission channel and is inoperative in respect of disturbance due to adjacent channels.